Brain Scan Technique Spots Alzheimer’s

March 26, 2008 -- A computer-assisted imaging technique that measures sugar metabolism within a critical area of the brain could hold the key to the early diagnosis of Alzheimer's disease and other dementias.

Researchers say that the technique was accurate 94% of the time in distinguishing Alzheimer's disease from other dementias in a newly reported study published in the March issue of the Journal of Nuclear Medicine.

It was also able to identify brain patterns associated with very early cognitive decline, raising hopes that the imaging model might lead to earlier diagnosis and better outcomes among patients with Alzheimer's and other dementias, says study researcher?Lisa Mosconi, PhD.

"Because the incidence of (Alzheimer's and related disorders) is expected to increase dramatically as the baby boomer generation ages, accurate diagnosis is extremely important -- particularly at the early and mild stages of dementia when lifestyle changes and therapeutic interventions would be most effective," Mosconi says.

Diagnosing Alzheimer's Disease

Mosconi and colleague Mony de Leon, EdD, both of New York University's Center for Brain Health, developed the brain scan-based computer program after identifying key changes in the part of the brain known as the hippocampus early in the course of Alzheimer's disease.

Specifically, they found that the hippocampus, which is associated with learning and memory, metabolizes glucose less efficiently as dementia progresses. Glucose is the fuel that allows the brain to function properly.

Using positron emission tomography (PET), the researchers were able to highlight glucose consumption patterns within the hippocampus and identify specific images associated with normal brain function, mild cognitive impairment, and different types of dementia, including Alzheimer's.

Their latest study included 548 people examined at seven separate centers who were mostly in their 60s and 70s. The participants had either no evidence of cognitive decline, mild cognitive impairment, Alzheimer's disease, or dementia due to other causes, confirmed through a battery of neurological and psychological tests.

Each patient was injected with the radioactive isotope FDG, which mimicked glucose once it entered the body. After about 30 minutes researchers began taking pictures of the brain using PET imaging, and the images were later analyzed using the computer program developed at NYU.

By comparing images of the cerebral cortex at the brain's surface to those of the hippocampus deep within the brain, the researchers could accurately distinguish between patients with normal brain function and specific dementias, including Alzheimer's.

"We were even able to identify people with mild cognitive impairment that did not meet the criteria for dementia," Mosconi tells WebMD.

The computer-assessed imaging model also appeared to predict which type of dementia someone with mild cognitive impairment would eventually have.

'Missing Piece of the Puzzle'

Mosconi and colleagues are now evaluating follow-up data on the patients in the study to determine how accurate the imaging was at predicting their clinical course. The next step after this is to examine the imaging technique outside the clinical trials setting.

"Right now we can't say if the results will apply to the normal population, where confounding medical conditions are common," she says. "But that is certainly the hope."

Society for Nuclear Medicine President Sandy McEwan, MD, tells WebMD that the NYU research represents a potentially seminal advance in the use of imaging for the early diagnosis of Alzheimer's and other dementias.

He says the fact that the imaging was conducted at different centers within the United States and Europe shows that the technique is reproducible in the clinical setting.

"This may be the piece of the puzzle that we have been missing," he says.